Protecting free OS extension from use with proprietary OS

[pgraf at q40.de]

On 21 Dec 2004 at 20:29, Chuck Swiger wrote:

[snip]

> If you want to prevent the end-users of the proprietary OS version from
> getting and using your software, that's a different story altogether.  Once
> you've published an open source project publicly on the net, it's out
> there. People who use the proprietary OS are going to be able to build use
> your module for themselves, without needing to redistribute your software
> to anyone else, and it would be hard to prove that any financial loss has
> occurred.

Thanks for your reply. It is not my concern that people could privately 
modify and build my software so it works with the commercial OS for 
themselves. I wouldn't be glad about it (I'd prefer they spend their time 
using and improving the free OS) but I'd tolerate it. My concern begins 
when it comes to redistribution (of a modified version of my software for 
the purpose of extending a proprietary OS). I want this only to be allowed 
if the OS is distributed as free software, too.

[snip]

> The other concern you seem to have has to do with how the software
> interacts, and whether that interaction forms a derivative work or merely
> an aggregation or compilation of software.

I think this is the point.

> For simple examples, a
> dynamicly loadable kernel module or shared library would result in a
> derivative work.  If the software in question is separate enough to run by
> itself as a distinct process, then the GPL would likely not apply.

I'll try to be more precise, although this is hard without going into
the technical peculiarities of the somewhat unusual OS: My extension will 
be part of the free OS, running in the same address space, and the free OS 
will have new system calls that jump into my code. My extension is _not_ a 
user application, it is technically part of the OS. But it could be 
separated so it is no longer statically linked (I might even have to do 
this separation myself for ROM size limitations).

I think the term "dynamicly loadable kernel module" would fit, although
this term is not in use in my hobbyist scene, and there is little
understanding of free software licensing also. For example when the
free OS was released under the GPL, a trader who sells the commercial
OS considered in _public_ that his fellow developers could now take
the "best of" the free code and merge it into the commercial OS.
I don't fear that such a blatant violation of the GPL happens, but a more
subtle one, where free and non-free binaries are kept separate and forming
the derivative work is not so easy to see.

I could have problems to communicate that two separately loaded binaries
can form a derivative work.

Could I accompany the GPL with an explanation what "derivative work"
means?

[snip]

Many thanks,
Peter